Automotive display control panel technology is moving from traditional non-interactive displays and mechanical switches to touch-sensitive screens and electronic sensing switches. One type of sensing switch is commonly referred to as a capacitive sensing switch. The capacitive sensing switch typically includes an electrode adapted to create an electric field adjacent thereto which generally defines a sensing zone. The electrode is coupled to a rear surface of a non-electrically conductive or a low-electrically conductivity panel, wherein the electrode is in electrical communication with sensing circuitry or a controller. When a conductive or a charged object such as a finger of a person, for example, is placed within the sensing zone on a front surface of the panel, the finger interacts with the electrical field and changes the capacitance of the electrode. The changed capacitance is detected by the sensing circuitry, indicating the occurrence of a switching event.
Electrically conductive panels are known to spread the electrical field from the electrode which reduces the sensitivity of the capacitive sensing switch within the desired sensing zone. Further, spreading the electric field extends the overall area of the sensing zone of the capacitive sensing switch which can result in undesirable switching performance. This is also present with the use of electrically conductive decorative finishes disposed on a surface of a control panel.
It is often desired to use the capacitive sensing switch with electrically conductive panels or panels having electrically conductive decorative finishes thereon. For example, electrically conductive decorative finishes are often employed with control panels to provide a desired aesthetic appearance to a passenger compartment for an automobile. When such electrically conductive decorative finishes have been used, the spreading of the electrical field of the electrode has been reduced by electrically isolating the portion of the panel within the sensing zone from the remainder of the panel and grounding the remainder of the panel. However, electrically isolating the portion of the panel within the sensing zone can cause unwanted performance characteristics in the capacitive sensing switch and produce an unwanted aesthetic appearance on the front surface of the panel.
The current method for adding capacitive sensing to a user interface surface requires several discrete parts. For example, a metal or conductive piece is typically secured to the rear of a traditional user interface (button) and a dedicated electrical interface provides electrical communication to a circuit board that contains the requisite electronic circuits and microcontrollers.
It would be desirable to develop a proximity sensor including a conductive elastomer portion and a non-conductive elastomer portion cooperating to sense a touch of a user, wherein the proximity sensor represents a plurality of controlled trigger events.